POSITION OF THE AMERICAN DIETETIC ASSOCIATION: VEGETARIAN DIETS (1993)
A considerable body of scientific data suggests positive relationships
between vegetarian diets and risk reduction for several chronic
degenerative diseases and conditions, including obesity, coronary artery
disease, hypertension, diabetes mellitus, and some types of cancer.
POSITION STATEMENT
It is the position of The American Dietetic Association that vegetarian
diets are healthful and nutritionally adequate when appropriately
planned.
VEGETARIANISM IN PERSPECTIVE
There is no single vegetarian eating pattern. The vegetarian diet is
mainly plant foods: fruits, vegetables, legumes, grains, seeds, and
nuts. Eggs, dairy products, or both may be included as well. The
lactovegetarian diet is fruits, vegetables, grains, dairy foods, and
their products whereas the lacto-ovovegetarian diet also adds eggs. The
vegan, or total vegetarian, diet completely excludes meat, fish, fowl,
eggs, and dairy products. Even within specific classifications of the
diet, considerable variation may exist in the extent to which animal
products are avoided. Therefore, individual assessment is required in
order to accurately evaluate the nutritional quality of a given diet.
Studies of vegetarians indicate that they often have lower mortality
rates from several chronic degenerative diseases than do nonvegetarians
(1,2). These effects may be attributable to diet as well as to other
lifestyle characteristics such as maintaining desirable weight, regular
physical activity, and abstinence from smoking, alcohol, and illicit
drugs.
In addition to possible health advantages, other considerations that may
lead to the adoption of a vegetarian diet include environmental or
ecological concerns, world hunger issues, economic reasons,
philosophical or ethical reasons, and religious beliefs.
IMPLICATIONS FOR HEALTH PROMOTION
Mortality from coronary artery disease is lower in vegetarians than in
nonvegetarians (1,2). Total serum cholesterol and low-density
lipoprotein cholesterol levels are usually lower, whereas high density
lipoprotein cholesterol and triglyceride levels vary, depending on the
type of vegetarian diet followed (3,4). Low-fat, low-cholesterol
vegetarian diets may decrease levels of apoprotein A, B, and E; alter
platelet composition and platelet function; and decrease plasma
viscosity. One study demonstrated reversal of even severe coronary
artery disease without the use of lipid lowering drugs by using a
combination of a vegetarian diet deriving less than 10% of its energy
from fat, smoking cessation, stress management, and moderate exercise
(3). Vegetarians have lower rates of hypertension (5) and
non-insulin-dependent diabetes mellitus than do nonvegetarians;
lessening these risk factors may also decrease the risk of
cardiovascular and coronary artery disease in the vegetarian population.
Seventh-Day Adventist vegetarians have lower rates of mortality from
colon cancer than the general population (6). This may be attributable
to dietary differences that include increased fiber intake; decreased
intake of total fat, saturated fat, cholesterol, and caffeine; increased
intake of fruits and vegetables; and, in lactovegetarians, increased
intakes of calcium. The dietary differences, especially in vegans, may
produce physiologic changes that may inhibit the causal chain for colon
cancer (7). Reduced consumption of meat and animal protein has also been
associated with decreased colon cancer in some, but not all, studies of
omnivores. Lung cancer rates are lower in vegetarians, chiefly because
they usually do not smoke, but possibly also because of diet (8).
Research suggests that vegetarians are also at decreased risk for breast
cancer (9).
Obesity, a major public health problem in the United States, exacerbates
or complicates many diseases. Vegetarians, especially vegans, often have
weights that are closer to desirable weights than do nonvegetarians
(10).
Vegetarians may be at lower risk for non-insulin-dependent diabetes
because they are leaner than nonvegetarians. Also, vegetarians' high
intake of complex carbohydrates, which are often relatively high in
fiber content, improves carbohydrate metabolism and may lower basal
blood glucose levels (11).
NUTRITION CONSIDERATIONS
Plant sources of protein alone can provide adequate amounts of the
essential and nonessential amino adds, assuming that dietary protein
sources from plants are reasonably varied and that caloric intake is
sufficient to meet energy needs. Whole grains, legumes, vegetables,
seeds, and nuts all contain essential and nonessential amino adds.
Conscious combining of these foods within a given meal, as the
complementary protein dictum suggests, is unnecessary. Additionally, soy
protein has been shown to be nutritionally equivalent in protein value
to proteins of animal origin and, thus, can serve as the sole source of
protein intake if desired (12).
Although most vegetarian diets meet or exceed the Recommended Dietary
Allowances (13) for protein, they often provide less protein than
nonvegetarian diets. This lower protein intake may be associated with
better calcium retention in vegetarians and improved kidney function in
individuals with prior kidney damage. Further, lower protein intakes may
result in a lower fat intake with its inherent advantages, because foods
high in protein are frequently high in fat also.
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Suggested
Food group daily servings Serving sizes
---------- -------------- -------------
Breads, cereals, 6 or more 1 slice bread
rice, and pasta 1/2 bun, bagel, or English muffin
1/2 cup cooked cereal, rice, or
pasta
1 oz dry cereal
Vegetables 4 or more 1/2 cup cooked or 1 cup raw
Legumes and other 2 to 3 1/2 cup cooked beans
meat substitutes 4 oz tofu or tempeh
8 oz soy milk
2 Tbsp nuts or seeds (these tend to
be high in fat, so use sparingly
if you are following a low-fat
diet)
Fruits 3 or more 1 piece fresh fruit
3/4 cup fruit juice
1/2 cup canned or cooked fruit
Dairy products Optional- up 1 cup low-fat or skim milk
to 3 servings 1 cup low-fat or nonfat yogurt
daily 1 1/2 oz low-fat cheese
Eggs Optional -- 1 egg or 2 egg whites
limit to 3 to
4 yolks per week
Fats, sweets, Go easy on Oil, margarine, and mayonnaise
and alcohol these foods Cakes, cookies, pies, pastries,
and beverages and candies
Beer, wine, and distilled spirits
Daily food guide for vegetarians. Source: Eating Well--The Vegetarian
Way. Chicago, Ill: American Dietetic Association; 1992.
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Plant carbohydrates are usually accompanied by liberal amounts of
dietary fiber. This is in contrast to animal products, which are devoid
of fiber. Fiber has been shown to be important in the prevention and
treatment of certain conditions and diseases.
Vegetarian diets that are low in animal products are typically lower
than nonvegetarian diets in total fat, saturated fat, and cholesterol,
factors associated with reduced risk of coronary artery disease and some
forms of cancer.
Adequate iron nutriture depends on both the amount of dietary iron
consumed and the amount absorbed. Inhibitors and enhancers affect the
absorption of nonheme iron, the form of iron found in plants. However,
inhibitors and enhancers can offset each other when a variety of foods
is consumed. Vegetarians are not at greater risk of iron deficiency than
nonvegetarians, but Western vegetarians generally have better iron
status than those in developing countries. Western vegetarians generally
have an adequate intake of iron from plant products. They also consume
greater amounts of ascorbic acid, an important enhancer of nonheme iron
absorption. In contrast, vegetarians in developing countries rely on
food staples that are low in iron; consume less ascorbic acid; and
consume more tea, which contains tannin, an inhibitor of iron
absorption.
The Recommended Dietary Allowance (13) for vitamin B-12 is minute.
Vitamin B-12 is produced by microorganisms present in the guts or
gastrointestinal tracts of animals and human beings, as well as in dirt
on the surface of unwashed plants. Vitamin B-12 is found in all animal
products; hence, a pattern that includes animal products such as milk
and milk products is unlikely to be deficient in vitamin B-12. Bacteria
produce vitamin B-12 in the human gut, but it appears to be produced
beyond the ileum, the site of vitamin B-12 absorption in the intestine
(14).
Lack of intrinsic factor in the stomach, rather than diet, however, is
the most common cause of vitamin B-12 deficiency. Atrophic gastritis,
with the consequent bacterial overgrowth of the upper gut, may also
contribute to vitamin B-12 deficiency, especially in the elderly. Plants
provide no vitamin B-12. In countries where sanitation is poor, vegans
may derive vitamin B-12 from foods that are contaminated with microbes
and organisms that produce the vitamin, such as on the surfaces of
unwashed fruits or vegetables. In Western countries, however, where
sanitary practices are better, the risk of vitamin B-12 deficiency for
vegans may be greater.
Vegans should include a reliable source of the vitamin in their diets.
Spirulina, seaweed, tempeh, and other fermented foods are not reliable
sources of vitamin B-12. As much as 80% to 94% of the so-called vitamin
B-12 in these foods, as measured by microbiological assay, may be
inactive analogs. Cyanocobalamin, the form of vitamin B-12 that is
physiologically active for human beings, is available from vitamin
supplements or fortified foods such as some commercial breakfast
cereals, soy beverages, some brands of nutritional yeast, and other
products.
Certain plant constituents appear to inhibit the absorption of dietary
calcium, but within the context of the total diet, this effect does not
appear to be significant. Calcium from low-oxalate vegetable greens,
such as kale, has been shown to be absorbed as well or better than
calcium from cow's milk (15). Calcium deficiency in vegetarians is rare,
and there is little evidence to show that calcium intakes below the
Recommended Dietary Allowance (13) cause major health problems in the
vegetarian population. The relatively high US recommendations for
calcium intake, compared with those for populations consuming a more
plant based diet, are designed to compensate for the calciuric effect of
high intakes of animal protein, which are customary in the United
States. Studies have shown that vegetarians, on the other hand, absorb
and retain more calcium from foods than do nonvegetarians (16,17).
Zinc is necessary for proper growth and development. Good plant sources
include grains, nuts and legumes. Western vegetarians usually have
satisfactory zinc status (18).
GROUPS WITH SPECIAL NEEDS
Infants, children, and adolescents who consume well-planned vegetarian
diets can generally meet all of their nutritional requirements for
growth (19,20). Those who follow vegan or veganlike diets should consume
a reliable source of vitamin B-12 and should have a reliable source of
vitamin D. Calcium, iron, and zinc intakes may also deserve special
attention, although intakes are usually adequate when reasonable variety
and adequate energy are consumed.
If exposure to sunlight is limited, the need for vitamin D
supplementation should be assessed. Because vegan diets tend to be high
in bulk, care should be taken to ensure that caloric intakes are
sufficient to meet energy needs, particularly in infancy and during
weaning. Both vegetarians and nonvegetarians whose infants are premature
or solely breastfed beyond 4 to 6 months of age should provide
supplements of vitamin D, if exposure to sunlight is inadequate, and
iron from birth or at least by 4 to 6 months of age (21).
Well-planned vegetarian diets can be adequate for pregnant and lactating
women. Vegetarians and nonvegetarians alike are generally advised to
take iron and folic acid supplements during pregnancy, although
vegetarians frequently have greater intakes of those nutrients than do
nonvegetarians. A regular source of vitamin B-12 is recommended for
vegans during pregnancy and lactation (21,22). A vitamin D supplement
should be taken by pregnant and lactating vegans if exposure to sunlight
is inadequate. Consumption of a variety of foods and adequate energy
will help ensure adequate intakes of calcium, iron, and zinc.
MEAL PLANNING
In planning vegetarian diets of any type, one should choose a wide
variety of foods and ensure that the caloric intake is adequate to meet
energy needs (23). (See the Figure.) Additionally, the following
recommendations are in order.
* Keep the intake of low nutrient-dense foods, such as sweets and fatty
foods, to a minimum. -- Choose whole or unrefined grain products,
instead of refined products, whenever possible, or use fortified or
enriched cereal products.
* Use a variety of fruits and vegetables, including a good food source
of vitamin C.
* If milk or dairy products are consumed, use low-fat or nonfat
varieties.
* Limit egg intake to 3 to 4 yolks per week.
* Vegans should have a reliable source of vitamin B-12, such as some
fortified commercial breakfast cereals, fortified soy beverages, or a
cyanocobalamin supplement. A vitamin D supplement may be indicated if
exposure to sunlight is limited.
* Vegetarian and nonvegetarian infants who are solely breastfed beyond
4 to 6 months of age should receive supplements of iron and vitamin D
if exposure to sunlight is limited.
The Dietary Guidelines for Americans (24) recommend a reduction in fat
intake and an increased consumption of fruits, vegetables, and whole
grains. Well-planned vegetarian diets can effectively meet these
guidelines and can be a health-supporting dietary alternative.
References
1. Burr ML, Butland BK. Heart disease in British vegetarians. Am J Clin
Nutr. 1988; 48:830-832.
2. Fraser GE. Determinants of ischemic heart disease in Seventh-Day
Adventists: a review. Am J Clin Nutr. 1988;48:833-836.
3. Ornish D, Brown S, Scherwitz L, Billings J, Armstrong W, Ports T,
McLanahan S, Kirkeeide R, Brand R, Gould KL. Can lifestyle changes
reverse coronary heart disease? Lancet. 1990;336:129-133.
4. Kestin M, Rouse I, Correll R, Nestel P. Cardiovascular disease risk
factors in free-living men: comparison of two prudent diets, one based
on lactoovovegetarianism and the other allowing lean meat. Am J Clin
Nutr. 1989;50:280-287.
5. Beilin, LJ, Rouse IL, Armstrong BK, Margetts BM, Vandongen R.
Vegetarian diet and blood pressure levels: incidental or causal
association? Am J Clin Nutr. 1988;48:806-810.
6. Phillips R, Snowdon D. Association of meat and coffee use with
cancers of the large bowel, breast, and prostate among Seventh-Day
Adventists: preliminary results. Cancer Res. 1983;45 (suppl):2403-2408.
7. Turjiman N, Goodman GT, Jaeger B, Nair PP. Diet, nutrition intake and
metabolism in populations at high and low risk for colon cancer:
metabolism of bile acids. Am J Clin Nutr. 1984;4:937.
8. Colditz G, Stampfer M, Willet W. Diet and lung cancer: a review of
the epidemiological evidence in humans. Arch Intern Med. 1987;147:157.
9. Chen J, Campbell TC, Li J, Peto R. In: Diet, Life-style and Mortality
in China. A study of the characteristics of 65 Counties. Oxford
University Press, Cornell University Press, and the China People's
Medical Publishing House; 1990.
10. Bergan JC, Brown PT. Nutritional status of "new" vegetarians. J Am
Diet Assoc. 1980;76:151-155.
11. Nieman DC, Underwood BC, Sherman KM, Arabatzis K, Barbosa JC,
Johnson M, Shultz TD. Dietary status of Seventh-Day Adventist vegetarian
and non-vegetarian elderly women. J Am Diet Assoc. 1989;89:1763-1769.
12. Young VR. Soy protein in relation to human protein and amino acid
nutrition. J Am Diet Assoc. 1991;91:828-835.
13. Food and Nutrition Board. Recommended Dietary Allowances. 10th ed.
Washington, DC: National Academy Press; 1989.
14. Herbert V. Vitamin B-12: plant sources, requirements, assay. In:
Mutch PB, Johnston PK, eds. First International Congress on Vegetarian
Nutrition. Am J Clin Nutr. 1988; 48:452.
15. Heaney R, Weaver C. Calcium absorption from kale. Am J Clin Nutr.
1990;51:656.
16. Zemel M. Calcium utilization: effect of varying level and source of
dietary protein. Am J Clin Nutr. 1988;48:880.
17. Marsh A, Sanchez T, Michelsen O, Chaffee F, Fagal S. Vegetarian
lifestyle and bone mineral density. Am J Clin Nutr. 1988;48:837-841.
18. Hambige K, Casey C, Krebs N. Zinc. In: Mertz W, ed. Trace Elements
in Human and Animal Nutrition. Vol 2. 5th ed. Orlando, Fla: Academic
Press; 1986.
19. Sabate J, Lindsted K, Harris R. Sanchez A. Attained height of
lacto-ovo vegetarian children and adolescents. Eur J Clin Nutr.
1991;45:51-58.
20. O'Connell J, Dibley M, Sierra J, Wallace B, Marks J, Yip R. Growth
of vegetarian children: the Farm study. Pediatrics. 1989;84:475-480.
21. Food and Nutrition Board, Institute of Medicine. Nutrition During
Lactation. Washington, DC: National Academy Press; 1991.
22. Food and Nutrition Board, Institute of Medicine. Nutrition During
Pregnancy. Washington, DC: National Academy Press; 1991.
23. Eating Well--The Vegetarian Way. Chicago, Ill: American Dietetic
Association; 1992.
24. Nutrition and Your Health: Dietary Guidelines for Americans. 3rd ed.
Washington, DC: US Dept of Agriculture and US Dept of Health and Human
Services; 1990.
* ADA Position adopted by the House of Delegates on October 18, 1987,
and reaffirmed on September 12, 1992. The update will be in effect until
October 1997.
* Recognition is given to the following for their contributions:
Authors:
Suzanne Havala, MS, RD; Johanna Dwyer, DSc, RD
Reviewers:
Phyllis Acosta, RD; Patricia Johnston, DrPH, RD; Mary
Clifford, RD; Vegetarian Nutrition dietetic practice group: Winston
Craig, PhD, RD, and Virginia Messina, MPH, RD; Pediatric Nutrition
dietetic practice group
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This position paper was "reprinted" from Journal of the American
Dietetic Association, November 1993, Volume 93, Number 11.